Compact Dual-LED Packaging With a 3-D Free-Form Lens for Uniform Rectangular Illumination

This paper presented a novel silicon-based dual light-emitting-diode (LED) packaging module with a 3-D freeform lens, using a silicon micromachined substrate and silicone dispensing process to achieve uniform rectangular illumination. The specific encapsulated lens was formed by using the interaction of the interfacial tension between the silicone material and a petal-like submount substrate at an appropriate curing temperature. Lens shaping and its optical characteristics were simulated and evaluated using Surface Evolver and TracePro software, respectively. The simulation results showed that the surface profile of the lens structure was highly dominated by the boundary conditions of a petal-like structure. Experiments demonstrated a typical free-form lens with a sag height of 2.8 mm and a convex-top curvature of 1.4 mm formed when a volume of 15 mm
³
silicone encapsulation was dispensed onto the petallike substrate with an inscribed rectangle of 2 × 4 mm
²
. When applying a driving current of 0.1 A on the packaged LED, the projected lighting patterns at a distance of about 0.8 m presented a rectangle-like shape with good uniformity at a large projection size of 1.7 × 0.7 m
²
. These results confirmed that this approach could be applied to dual-LED packaging and implied that uniform rectangular illumination is suitable for indoor applications with improved lighting efficiency.